To make the candied lemon topping: Slice 1 1/2 lemons into very thin rings (if you have a mandoline, now is the time to use it). Tease out any seeds. Juice the remaining 1/2 lemon and set aside. Bring a small pot of water to a boil, add the lemon slices, and cook for 1 minute. Use a slotted spoon to transfer them to an ice bath. Bring 1 cup (198g) sugar, 1 cup (227g) water, and the reserved lemon juice to a boil, stirring to dissolve the sugar. Lower to a bare simmer, add the lemon slices, and simmer very gently for 45 minutes to 1 hour, stirring occasionally, until the slices are translucent, with no white bits remaining. Use a slotted spoon to transfer to a parchment-lined baking sheet to cool. For best results, store in an airtight container and use within 1 day. (Save the lemon jelly left in the pot for spreading over toast or mixing into yogurt.